Radiation shielding means joint and method of making same

ABSTRACT

A pair of radiation shielding members such as uranium castings are provided with tapered end portions which are positioned adjacent one another. The joint between the radiation shielding members includes a plurality of filler members disposed between said tapered portions and the filler members being positioned in contact with one another and radially outwardly of one another, the outer ones of said filler members overlapping inner ones of said filler members in a longitudinal direction. The filler members are welded to the tapered ends of the radiation shielding members along the opposite circumferentially extending edges of the filler members.

United Sta Bush, Jr.

[ 11 3,751,669 1 Aug. 7, 1973 RADIATION SHIELDING MEANSJQLET AND METHOD OF MAKING SAME d n a r e .m C .h S l 6 M1 F. in mm Or. BF m .wm hh PM L an .m% mm X E W mm 0 PA Jay D. Gordon [75] Inventor: Fred J. Bush, .lr., Malvern, Pa.

[57] ABSTRACT A pair of radiation shielding members such as uranium [73] Assignee: NL Industries, Inc., New York, NY.

Filed: May 24, 1971 castings are provided with tapered end portions which are positioned adjacent one another. The joint between the radiation shielding members includes a pl Appl. No.: 146,356

urality of U.S. Cl. filler members disposed between said tapered portio ns and the tiller members being positioned in contact with one another and radially outwardly of one another, the

60S m /w w 5H 22 R m8 .1 u/ 0 n5 n2 mh c r. a .e "S m n e mF HUM 555 outer ones of said filler members overlapping inner ones of said filler members in a longitudinal direction.

[56] References Cited UNITED STATES PATENTS The filler members are welded to the tapered ends of 250 08 R the radiation shielding members along the opposite cirzsoflos R cumferentially extending edges of the filler members.

3,119,933 1/1964 3,483,381 12/1969 Bonillaetal....................

14 Claims, 4 Drawing Figures & 5 m m 1 m m z RADIATION SHIELDING MEANS JOINT AND METHOD OF MAKING SAME BACKGROUND OF THE INVENTION The present invention relates to a joint between radiation shielding members as employed, for example, in shipping containers for spent fuel elements utilized in nuclear reactors and the like. Such shipping containers may be utilized for shipping any type of radioactive material and are especially adapted to ship irradiated nuclear fuel elements, such containers normally being mounted on railroad cars, trailers and the like for transport from one location to another.

The utilization of uranium shielding in shipping containers provides a considerable weight savings and accordingly substantially improves the economy of shipping fuel elements. A particular problem involved with such shipping containers is the fact that the uranium shielding is generally provided in the form of castings. The amount of shielding required in a shipping container usually exceeds the casting capacity, and accordingly it is necessary to join several castings in such shipping containers.

The radiation shielding members must be joined in such a manner that adequate radiation protection is provided both under normal and accident conditions. The joint must therefore be of very high integrity so that in the event theshipping container is accidentally damaged, the castings comprising the radiation shielding members will not separate at the interfaces between the cast sections and allow radiation streaming.

The present invention is directed to a joint between radiation shielding members which provides adequate strength and shielding integrity while also affording a high degree of manufacturing convenience. The rigid metal shielding comprising a plurality ofjoined castings must be able to take severe impact loadings developing tension, compression and shear stresses of considerable magnitude. The joints between the castings must accommodate such loadings in all directions.

The logical solution to joining of a pair of cylindrical uranium castings in view of conventional welding techniques would be to provide tapered ends on the two castings and interconnect such ends with a full penetration weld of generally triangular cross-sectional configuration. However, such a full penetration weld cannot be successfully performed with uranium castings having a thickness on the order of 4 to inches.

SUMMARY OF THE INVENTION The pair of radiation shielding members to be joined are provided with tapered end portions disposed adjacent to one another. A plurality of filler members are provided, these filler members being disposed in the joint between the tapered end portions of the radiation shielding members, the filler members being welded to such tapered end portions along the opposite circumferentially extending edges of the filler members.

Each of these filler members has a thickness substantially less than the thickness of the radiation shielding members to be joined, the filler members being disposed radially outwardly of one another. Radially outwardly positioned filler members overlap radially inwardly positioned filler members and extend therebeyond in a longitudinal direction, such filler members fitting within the tapered end portion of the radiation shielding members, the remaining space between the radiation shielding members being filled with weld material.

With the construction of the present invention, radiation shielding members in the form of radiation castings can be successfully welded to one another since it is possible to perform a plurality of relatively small welds with present technology, whereas a single large weld could not be successfully produced. Additionally, it is more economical to perform the weld construction of the present invention since less weld rod is required which is very expensive, and furthermore less labor is involved since less weld material and time is required in making the weld.

The completed joint of the present invention provides adequate strenght and shielding intergrity even when subjected to severe impact loads as may occur under accidental conditions.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a vertical longitudinal section through a shipping container incorporating joints between the radiation shielding members thereof according to the present invention;

FIG. 2 is an enlarged view of a portion of the structure shown in FIG. 1;

FIG. 3 is a view similar to FIG. 2 illustrating a modification of the present invention; and

FIG. 4 is a view similar to FIG. 2 illustrating still another form of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawing wherein like reference characters designate corresponding parts throughout the several views, a first form of the invention is illustrated in FIGS. 1 and 2. As seen in FIG. 1, a shipping container includes an inner shell means 10 having a bottom 12 and an outer shell means 14 having a bottom 16, the shell means being formed of a suitable material such as stainless steel or the like. A plurality of spaced annular horizontally disposed cooling fins 18 are secured to the outer surface of the outer shell means 14. Radiation shielding means is provided between the inner and outer shell means and as illustrated includes three uranium castings 20, 22 and 24 which are cast separately from one another and which are joined in the finished construction by a pair of joints indicated generally by reference numerals 26 and 28. In this construction, each of the castings is of generally cylindrical configuration, the castings being joined end to end with one another with the joints extending circumferentially around the radiation shielding means.

A central radioactive material receiving cavity 30 is provided within the shipping container, and the open end of the shipping container is closed 011' by a conventional closure means or head 32 held in place with respect to the associated body means by a plurality of cap screws 34 extending through suitable holes provided in the closure means and being threaded into correspondingly threaded holes provided in the body means.

As seen in FIG. 2, the end portions of each of castings 22 and 24 are tapered and are stepped so as to provide a first series of annular shoulders 40, 42 and 44 on casting 22 as well as a corresponding series of annular shoulders 46, 48 and 50 on casting 24.

When making the joint shown in FIG. 1, the tapered end portions of castings 22 and 24 are first placed in adjacent relationship to one another as shown and weld 52 is made completely around the circumference of the two castings so as to join the inner portions of the castings to one another. A filler member or ring 54 is then placed in the position shown so as to rest on circumferentially extending shoulders 40 and 46. Filler member 54 may comprise two or more circumferentially extending parts so that it may be readily inserted in the position illustrated. This filler member as well as the remaining filler members to be described is ofa thickness substantially less than the thickness of the radiation shielding members 22 and 24 and is formed along an arc so as to fit snugly about the shoulders formed on the radiation shielding members. Filler member 54 is then secured in operative position by forming welds 56 and 58 along the opposite circumferentially extending edges of the filler member to weld the filler member to the adjacent radiation shielding members.

A further filler member 60 is then placed in the operative position shown resting on shoulders 42 and 48 and also engaging filler member 54 previously described. Filler member 60 may also be formed as two or more circumferentially extending pieces, the filler member then being secured in position by forming welds 62 and 64 along the opposite circumferentially extending edges thereof to weld the filler member to the adjacent radiation shielding members.

Still another filler member 66 is then inserted in the operative position shown resting against shoulders 44 and 50 and also engaging filler member 60 previously described. Here again, the filler member may comprise two or more circumferentially extending pieces, the filler member being secured in operative position by forming welds 68 and 70 along the opposite circumferentially extending edges thereof to weld the filler member to the adjacent radiation shielding members. It will be noted that filler member 60 overlaps and extends longitudinally beyond opposite edges of filler member 54, and likewise filler member 66 overlaps and extends longitudinally beyond opposite edges of filler member 60 so that radially outwardly ones of said filler members overlap radially inwardly ones of said filler member throughout the joint.

When a joint is formed in the manner as shown in FIG. 2 wherein there are in effect four layers of welds, the weld metal required is only 7/28 of the weld metal required in a full penetration weld of corresponding size. If five layers are employed, only 9/45 as much weld metal is required as a corresponding full penetration weld, and if six layers are employed, only 11/66 as much weld metal is required as a corresponding full penetration weld. It is apparent that by providing a plurality of layers including filler member according to the present invention, important economies in manufacture are obtained. The filler members in each case are preferably of the same material as the radiation shielding members to provide an effective joint.

The filler members in all forms of the invention must each be made of two or more preformed pieces in order to enable the filler members to be placed in the desired positions.

Referring now to FIG. 3 of the drawing, a modified form of the invention is illustrated which is similar to that shown in FIG. 2 and similar parts have been given the same reference numerals primed. The only difference in the joint shown in FIG. 3 from that shown in FIG. 2 is the fact that the end surfaces 80 and 82 of castings 22' and 24' are formed as smoothly sloping surfaces rather than stepped surfaces as in the previous embodiment.

The joint is otherwise made in the same manner as the joint previously described, the joint shown in FIG. 3 providing the same benefits as the joint shown in FIG.

Referring now to FIG. 4 of the drawing, still another form of the invention is illustrated wherein parts similar to those shown in FIG. 2 have been given the same reference numerals double primed. In this form of the invention, the radially inward portion of the joint comprises a stepped interface between the two castings 22" and 24". Stepped interface increases the sheer strength of the joint and minimizes radiation streaming along the interfaces between the castings.

Stepped interface 90 also acts as an initial centering and locating means for the two castings. A circumferential weld 92 is then made to join the two radiation shielding members before the filler members are welded in place.

The end surfaces of the two castings are tapered and are stepped so as to provide circumferentially extending shoulders and 104 on casting 22" as well as circumferentially extending shoulders 102 and 106 on casting 24".

A first filler member 110 which may comprise two or more circumferentially extending pieces rests upon shoulders 100 and 102 and is secured in place by welds 112 and 114 formed along the opposite circumferentially extending edges-thereof to weld filler member 110 to the two castings.

A further filler member 116 which may also comprise two or more circumferentially extending pieces rests upon shoulders 104 and 106 and is in engagement with previous filler member 110. Filler member 116 is secured in position by welds 1 l8 and 120 extending along the opposite circumferentially extending edges thereof to weld filler member 116 to the adjacent castings.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, and since the scope of the invention is defined by the appended claims, all changes that fall within the metes and bounds of the claims or that form their functional as well as conjointly cooperative equivalents are therefore intended to be embraced by those claims.

What is claimed is:

l. A radiation shielding means joint comprising a pair of radiation shielding members to be joined end to end, the adjacent ends of said shielding members being of reduced thickness, a joint between adjacent ends of said shielding members, said joint including a pluraltiy of filler members and weld material connecting said filler members to adjacent ends of said radiation shielding members.

2. A joint as defined in claim I wherein said radiation shielding members are castings formed of uranium, said filler members also being formed of uranium.

3. A joint as defined in claim I wherein each of said radiation shielding members includes adjacent tapered portions connected to said filler members by said weld material.

4. A joint as defined in claim 1 wherein each of said radiation shielding members includes adjacent stepped portions connected to said filler members by said weld material.

5. A joint as defined in claim 1 wherein said radiation shielding members are tubular and are disposed in end to end relationship with respect to one another, said filler members extending peripherally of the end portions of said radiation shielding members.

6. A joint as defined in claim 1 wherein said filler members are disposed successively radially outwardly.

7. A joint as defined in claim 6 wherein said filler members are disposed adjacent one another.

8. A joint as defined in claim 6 wherein radially outer ones of said filler members overlap and extend beyond opposite sides of the radially inwardly filler members.

9. A joint as defined in claim 1 wherein the thickness of each of said filler members is substantially less than the thickness of said members.

10. A joint as defined in claim 1 wherein said radiation shielding members have stepped surfaces in engagement with one another to prevent radiation beaming, said stepped surfaces being disposed inwardly of said filler members.

11. The method of joining two radiation shielding members end to end comprising forming portions of reduced thickness on adjacent ends of said members and disposing said end portions of reduced thickness adjacent one another, placing filler means of a thickness less than the thickness of said radiation shielding members between said adjacent end portions, welding'said filler means to said adjacent end portions, placing further filler means of a thickness less than the thickness of said radiation shielding members between said adjacent end portions, and welding said further filler means to said adjacent end portions.

12. The method as defined in claim 11 wherein said further filler means is disposed radially outwardly of said first-mentioned filler means, each of said filler means being welded to said tapered portions along peripherally extending end edges of said filler means.

13. The method as defined in claim 11 including the step of welding said two radiation shielding members to one another along the tapered portions thereof throughout only a portion of the thickness of the radiation shielding members prior to placing said firstmentioned filler means between said tapered portions.

14. The method as defined in claim 11 wherein said shielding members are provided with stepped surfaces, placing said stepped surfaces in contact with one another, and then joining said shielding members to one another by a circumferential weld adjacent said stepped surfaces prior to placing a filler means between said portions. 

1. A radiation shielding means joint comprising a pair of radiation shielding members to be joined end to end, the adjacent ends of said shielding members being of reduced thickness, a joint between adjacent ends of said shielding members, said joint including a pluraltiy of filler members and weld material connecting said filler members to adjacent ends of said radiation shielding members.
 2. A joint as defined in claim 1 wherein said radiation shielding members are castings formed of uranium, said filler members also being formed of uranium.
 3. A joint as defined in claim 1 wherein each of said radiation shielding members includes adjacent tapered portions connected to said filler members by said weld material.
 4. A joint as defined in claim 1 wherein each of said radiation shielding members includes adjacent stepped portions connected to said filler members by said weld material.
 5. A joint as defined in claim 1 wherein said radiation shielding members are tubular and are disposed in end to end relationship with respect to one another, said filler members extending peripherally of the end portions of said radiation shielding members.
 6. A joint as defined in claim 1 wherein said filler members are disposed successively radially outwardly.
 7. A joint as defined in claim 6 wherein said filler members are disposed adjacent one another.
 8. A joint as defined in claim 6 wherein radially outer ones of said filler members overlap and extend beyond opposite sides of the radially inwardly filler members.
 9. A joint as defined in claim 1 wherein the thickness of each of said filler members is substantially less than the thickness of said members.
 10. A joint as defined in claim 1 wherein said radiation shielding members have stepped surfaces in engagement with one another to prevent radiation beaming, said stepped surfaces being disposed inwardly of said filler members.
 11. The method of joining two radiation shielding members end to end comprising forming portions of reduced thickness on adjacent ends of said members and disposing said end portions of reduced thickness adjacent one another, placing filler means of a thickness less than the thickness of said radiation shielding members between said adjacent end portions, welding said filler means to said adjacent end portions, placing further filler means of a thickness less than thE thickness of said radiation shielding members between said adjacent end portions, and welding said further filler means to said adjacent end portions.
 12. The method as defined in claim 11 wherein said further filler means is disposed radially outwardly of said first-mentioned filler means, each of said filler means being welded to said tapered portions along peripherally extending end edges of said filler means.
 13. The method as defined in claim 11 including the step of welding said two radiation shielding members to one another along the tapered portions thereof throughout only a portion of the thickness of the radiation shielding members prior to placing said first-mentioned filler means between said tapered portions.
 14. The method as defined in claim 11 wherein said shielding members are provided with stepped surfaces, placing said stepped surfaces in contact with one another, and then joining said shielding members to one another by a circumferential weld adjacent said stepped surfaces prior to placing a filler means between said portions. 